According to Khan, "Ra.One" means "Random Access - Version 1.0" while G.One means Good One. Ra.One also sounds like Raavan the mythological villain while G.One (Shahrukh's character) sounds like ...
Yet one villain surpasses them all as the Caped Crusader's greatest threat: Ra's al Ghul. Batman's career as Gotham's protector is often built on the assumption that he's the best at what he does.